The latest of ridiculous bugs I have found after my switchover to Mac is that Korean takes precedence over Japanese when “Automatic” is selected as the encoding on Mail.app. It literally sees Japanese text as Korean and encodes emails as ISO-2022-KR (Korean) if both Japanese and Korean are selected under Languages.

Try it yourself: make sure both Korean and Japanese are in the Languages list (so they show both show up in Mail.app’s Message > Text Encoding) and send an email containing Japanese text when encoding is set to “Automatic”. View the full message source and see that it encodes the message as ISO-2022-KR, not ShiftJIS or UTF-8 which it should. You have to completely remove Korean from the list if you want to use Automatic encoding, or manually select the encoding yourself every time. I cannot find a setting to force an encoding (er, UTF-8) on every email you send.

This is not a problem if the recipient is a PC/Mac user since the mail client will sort it out – but sending mails to a Japanese phone, which obviously has no idea what to do with Korean text encoding (and can’t suss out that its actually Japanese text) means that the lucky recipient gets 文字化け、mojibake, jumbled garbage.

Its even worse on the iPhone

If you ever decide to turn Korean keyboards on in the Language settings, or switch to Korean, iPhone appears to add Korean to the Languages list when choosing its own encoding. However, you cannot change the encoding manually on iPhone, or ever remove Korean from the list, even if you then disable Korean input.
The net result? You can never send Japanese mails to Japanese mobile phones ever again on your iPhone, until you do a full system restore. Which I am now doing. If you reply to a mail that was sent to you in ShiftJIS, the iPhone is at least clever enough to reply in the same encoding type but you are SOL if you want to compose a new one.
Rubbish. Windows Mobile has an option to “always send mail as UTF-8”. I wonder how many iPhone users in Japan have fallen foul of this?